Tun of JSCompiler for ng_tensorboard (#3281)
Tun of JSCompiler for ng_tensorboard (#3281)

Context:
- JSCompiler adds overhead to our builds.
- ng_tensorboard makes another Vulcanization bundle than regular
  TensorBoard.
- in CI, we build both Vulcanized bundles because we do `bazel build
  tensorboard/...`.

This change turns off Vulcanization for currently develop only
ng_tensorboard. This change does not impact our Pip package but only CI
and local development.
tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard